The most complex node is the "global city", with links binding it to other cities having a direct and tangible effect on global socio-economic affairs.[1] The term "megacity" entered common use in the late 19th or early 20th centuries; one of the earliest documented uses of the term was by the University of Texas in 1904.[2] The term "global city", rather than "megacity", was popularized by sociologistSaskia Sassen in her 1991 work, The Global City: New York, London, Tokyo.[3] "World city", meaning a city heavily involved in global trade, appeared in the May 1886 description of Liverpool, by The Illustrated London News.[4]Patrick Geddes later used the term "world city" in 1915.[5] More recently, the term has focused on a city's financial power and high technology infrastructure, with other factors becoming less relevant.[6][7]

Criteria

Global city status is considered beneficial and desirable. Competing groups have developed multiple alternative methods to classify and rank world cities and to distinguish them from non-world cities.[5] Although there is a consensus upon leading world cities,[8] the chosen criteria affect which other cities are included.[5] Selection criteria may be based on a yardstick value (e.g., if the producer-service sector is the largest sector then city X is a world city)[5] or on an imminent determination (if the producer-service sector of city X is greater than the combined producer-service sectors of N other cities then city X is a world city.)[5]

Cities can fall from ranking, as in the case of cities that have become less cosmopolitan and less internationally renowned in the current era.

Characteristics

Although criteria are variable and fluid, typical characteristics of world cities are:[9]

High-quality educational institutions, including renowned universities, international student attendance,[11] and research facilities

Multi-functional infrastructure offering some of the best legal, medical, and entertainment facilities in the country

High diversity in language, culture, religion, and ideologies.

Rankings

Global Economic Power Index

In 2015, the second Global Economic Power Index, a
meta list compiled by Richard Florida, was published by The Atlantic (distinct from a namesake list[12] published by the Martin Prosperity Institute), with city composite rank based on five other lists.[12][13]

Global Power City Index

The Institute for Urban Strategies at The Mori Memorial Foundation in Tokyo issued a comprehensive study of global cities in 2018. They are ranked based on six categories: economy, research and development, cultural interaction, livability, environment, and accessibility, with 70 individual indicators among them. The top ten world cities are also ranked by subjective categories including manager, researcher, artist, visitor and resident.[14]

GaWC study

A map showing the distribution of GaWC-ranked world cities (2010 data)

Jon Beaverstock, Richard G. Smith and Peter J. Taylor established the Globalization and World Cities Research Network (GaWC). A roster of world cities in the GaWC Research Bulletin 5 is ranked by their connectivity through four "advanced producer services": accountancy, advertising, banking/finance, and law.[8] The GaWC inventory identifies three levels of global cities and several sub-ranks,[15] although the authors caution that "concern for city rankings operates against the spirit of the GaWC project"[16] (emphasis in original).

The 2004 rankings added several new indicators while continuing to rank city economics more heavily than political or cultural factors. The 2008 roster, similar to the 1998 version, is sorted into categories of Alpha world cities (with four sub-categories), Beta world cities (three sub-categories), Gamma world cities (three sub-categories) and additional cities with High sufficiency or Sufficiency presence. The cities in the top two classifications in the 2018 edition are:[17]

Alpha ++

Alpha +

Global Cities Index

In 2008, the American journal Foreign Policy, in conjunction with the consulting firm A.T. Kearney and the Chicago Council on Global Affairs, published a ranking of global cities, based on consultation with Saskia Sassen, Witold Rybczynski, and others.[18]Foreign Policy noted that "the world’s biggest, most interconnected cities help set global agendas, weather transnational dangers, and serve as the hubs of global integration. They are the engines of growth for their countries and the gateways to the resources of their regions."[19] The ranking is based on 27 metrics across five dimensions: business activity, human capital, information exchange, cultural experience, and political engagement and was updated in 2010, 2012, 2014, 2015, 2016, and 2017. Since 2015 it has been published together with a separate index called the Global Cities Outlook: a projection of a city’s potential based on rate of change in 13 indicators across four dimensions: personal well-being, economics, innovation, and governance.[20]

The Wealth Report

"The Wealth Report" (a global perspective on prime property and wealth) is made by the London-based estate agent Knight Frank LLP together with the Citi Private Bank. The report includes a "Global Cities Survey", evaluating which cities are considered the most important to the world’s HNWIs (high-net-worth individuals, having over $25 million of investable assets). For the Global Cities Survey, Citi Private Bank’s wealth advisors, and Knight Frank’s luxury property specialists were asked to name the cities that they felt were the most important to HNWIs, in regard to: "economic activity", "political power", "knowledge and influence" and "quality of life".[21][22]